Manifold filling, without the boredom?
August 08, 2022

Manifold filling, without the boredom?

How do you fill a radiant system with the least amount of headache, in order to get the air out?  Should you flush through the boiler side?  What takes the least amount of time? When is a fill cart helpful?  Is street pressure water enough to properly purge?

In this episode, the guys share their field experience filling manifolds.  Just like toppings on a hot dog, there is no one specific way to do it that everyone will agree on.  Dan and Greg go over the hows and whys for the different approaches.  They mention the specifics for the various styles of Caleffi manifolds, including when to use the H-fitting on the 172 series products

Thanks for tuning in!

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Blog post comments
Tim O
September 08, 2022

Hi Gents, I have a new hydronic system with Caleffi Twist Flow Manifolds. It was installed last November and ran it through the first Winter and it performed very well. I'm flushing/refilling the system before the next heating season begins. A tiny bit of sediment and very brown water (Fernox?) remains in the Twist Flow flow meters. The water in it is very dark, rusty/brown and makes it difficult to see the meter flow marks. Even after flushing/filling with clean water, the flow meters aren't clearing the brown/rusty looking water. Is there a method to clear the meters without removing them?


In reply to by Tim O

December 25, 2022

Same here - one day Twist Flow flow meters contained rusty brown water making it almost impossible to see the meter flow marks. Strangely only occurs on the Twist Flow flow meter on one of the manifolds.


In reply to by Jason

January 09, 2023

The flow meters are a window into the system. It could be that the fluid quality has changed, rusty water potentially indicating continued air infiltration into the system. It is a good practice to check for a system leak, if the water color is changing. The frequency of zone cycling in different manifold locations could lead to some flow meters looking clearer than others.

September 08, 2022

Hello, I'm glad your manifold is performing well. Is the manifold mounted in an inverted application where the flow meters are pointing down? The flow meters will still work fine, in that case. However, sediment from the system fluid can settle there and obscure the ability to read the flow rate. The flow meters can be taken out and flushed in a sink to clear the debris. You would have to isolate the manifold and depressurize the loops to do that. They do have an o-ring seal, so they go back together easily. If the system was balanced well before the flushing/refilling, you could also just leave the sediment in there and save the task of getting the air out of the PEX again. Any other questions, feel free to give us a call at (414) 238-2360 ext 3370